i've used it, however I only put it in the gas tank and the intake manifold, i didn't put a 1/3 in the oil. I saw a little bit of white smoke and that was it. As far as feeling better, I really didn't see a large improvement. I will probably do it again sometime in the summer and throw some into the oil as well. I'm hoping to get the knocking gone, probably wishful thinking i won't lie